Ach

The Ach is a river in Upper Austria’s Innviertel region. It rises near Waldzell in the Kobernaußerwald at about 670 metres above sea level. After flowing north for two kilometres it turns northwest and continues for another thirty-six kilometres before joining the Inn just below Mühlheim. Locals sometimes call it the Waldzeller Ache, Mühlheimer Ache or Pollinger Ache depending on the stretch. The Ach carries an average of 5.24 cubic metres of water per second past Mamling. Its catchment covers 315 square kilometres, shared between the Braunau and Ried districts. The largest tributaries are the Mettmacher Ache, Altbach and Lochbach. The river’s flow stays fairly steady, rising only to 6.9 cubic metres per second in March and falling to 4.2–4.4 in September and October. The upper reaches remain close to their natural state, while the lower course has been straightened and reinforced with stonework. The mouth into the Inn is a man-made cut. Fish such as brown trout and bullhead live in the cleaner headwaters, while rainbow trout and grayling appear further downstream. The land around the Ach is mainly farmland, woodland and pasture, lightly settled but heavily used for livestock.